Do you smile a lot? If you're American, the answer is almost certainly yes. In a fascinating Atlantic article, Olga Khazan reveals that Americans are by a wide margin the most frequent smilers on Earth. Not only that, analysis of U.S. leaders compared with leaders from other countries shows that we smile bigger, wider, toothier smiles than our counterparts from other countries.

Why are we such a smiley bunch? One answer appears to be stability. In countries with more unstable histories, such as Russia, people are less likely to smile, at least at strangers. In stabler countries, people are more open and relaxed, and more likely to trust, and therefore smile at, someone they don't know.

Another reason is diversity. Researchers also found that in nations with large immigrant populations (such as the U.S.) people are much likelier to smile at strangers. It's not hard to figure out why. A high percentage of immigrants means a greater likelihood of a language barrier, and when you're face to face with strangers who can't speak your language and you can't speak theirs either, a smile is the quickest way to make it clear that you mean them no harm.

And there's our relentless emphasis on positive thinking. Researchers asked college students in 10 countries which emotions they liked to feel most often. Those where the students reported a high preference for happy, high-energy emotions also had government officials who tended to appear happy and excited in their photos. In other words, in certain nations including ours, a happiness-seeking culture leads to more frequent and bigger smiles.

Research shows that smiling can boost your immune system and extend your life, as well as making others trust you. So why would you ever think about smiling less? Because in some situations, excessive smiling is counterproductive. Here are some reasons you should consider stifling your smile:

1. You may confuse people from other cultures.

A smile doesn't mean the same thing to your international contacts that it does to you. One Finnish Reddit user posted in answer to a question that if a stranger smiled at him, he would assume that stranger was either insane or drunk--or American. There are definitely places and situations where excessive smiling can make the people you're interacting with uncomfortable, and you never want to do that. So if you're dealing across cultures, be sensitive to different smiling norms and take your cue from the people around you. In the same way, if someone from another culture fails to smile at you when an American would (when serving you in a shop, for example) don't assume they're being uncaring or hostile.

2. You appear insincere.

A " permasmile" can make people distrust you. Body language experts noted that Hillary Clinton, early in her campaign, tended to smile her way through entire televised debates, which many viewers found off-putting. If you're constantly smiling, you have nowhere to go when you genuinely want to express pleasure or gratitude. Don't leave a smile plastered to your face all the time.

3. It's the wrong moment for a smile.

My colleague John Brandon overheard a coffee shop clerk being scolded for not smiling at him. As it happened, he'd been complaining about a stale pastry at that moment, and a smile would have made him feel that she wasn't taking his complaint seriously. Americans, with our propensity to smile, have a bad tendency to grin when we shouldn't, such as when delivering bad news or criticism. If the timing is inappropriate for a smile, then just don't do it. Bite yourself in the tongue if you have to.

4. You're trying to project authority.

Some experts say that women undermine our power in the workplace by smiling too much. And indeed, in our culture, excessive smiling is the mark of a subordinate, especially if the person in front of us is not smiling at us.

There's some fascinating research that shows people in positions of power will return the smile of a subordinate, but are slower to smile at someone of equal status. Keep that in mind next time you're in a difficult negotiation, especially if you want to be seen as an equal. Smiling too much can send someone the wrong message about whether or not to take you seriously.